An overview in policy debate is part of a speech which is flagged as not responding to the line-by-line arguments on the flow. An overview may be "global" if presented at the beginning of a speech or "local" if presented at the beginning of a position.
Overviews typically list the order a debater's speech will be given in. For instance, On-Case, Co-op Disadvantage, Spending Disadvantage, Weapon Disadvantage would be an expected overview.
Debaters will usually inform the judge where they will be giving an overview before they start a speech because it can make it harder to flow the speech. A small minority of judges dislike this practice and will start speech time when a debater starts giving this order.
Many judges dislike overviews because, since many are scripted before the round begins, they tend to be non-responsive or repetitive and are often long. However, most judges and coaches support the practice for arguments which cannot be placed anywhere on the line-by-line or that need to be flagged for their importance.
The above is also informally known as a "road map"
Another form of an overview is of specifically in the section of the speech(i.e. Topicality, Kritik, Disadvantage, Counter-Plan, etc). This is commonly announced before the debater's speech and will signpost an overview.
The overview usually consists of star/main arguments being made and more than likely tend to contain extended evidence or authors. This practice is used to elaborate an argument and/or bring it back up in order for the judge to be aware of the main arguments being made by a team.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』